I do not believe for a second that Jazz is happy about his destroyed penis. This poor kid has suffered a life time of manipulation, gas lighting, and abuse. He was forced to endure this abuse while millions of viewers watched and cheered it on. Of course, he doesn't actually see it as abuse; he sees it as support. He grew up with millions of people showering him with attention, fame, money, and assuring him that this was what he really wanted and needed in order to be happy. I can't imagine how anyone who has been forced into this life since the age of 3 would be able to see that they are actually being abused for money and attention.
He had no chance to escape because any doubt he may have is met with his fucked up parents assuring him he's transgender. He's surrounded by fans and freaks that eat this shit up. He has TV agencies, magazines, and publishers pressuring him into getting the surgery because this train wreck is a massive cash cow no matter what the outcome of the surgery is.
Just imagine what went through this kid's head before he butchered his already fucked up micro penis. After years of being assured that he is a woman and that he will have a REAL vagina, of course he isn't going to forego the surgery. In his mind, all the fucked up shit he has gone through will be worth it after he has the surgery, because he will finally be a real girl and finally be happy. You can see it in one episode when he tells his grandma how excited he is to have sex and finally orgasm after he gets a vagina. Does anyone on the show ever tell this kid honestly that he is going to have a rotting hole in his body that can't tolerate pounding and friction like a real vagina can? Did anyone tell this kid that real women rarely even orgasm from vaginal penetration? Of course not.
Now imagine being Jazz after the operation and seeing your "vagina" falling apart. Imagine being in pain and seeing an infected gaping hole where your penis used to be. Who wouldn't go into deep denial mode? Who the hell would want to admit that your mother lied to you, that you wasted 15 years chasing a fantasy, and all you have to show for it is fucked up boobs and an obliterated crotch? Deep down he knows he made a huge mistake, but the reality is too painful to admit. So he latches on to his mommy for assurance that he is going to be okay and that eventually his vagina will work like a real one.
Even if he wanted to express a negative opinion, does anyone think his mother would ever allow it? What about the TRAs? No way would ever let Jazz, the poster child for trans children, utter a single negative word about his experience. Because that would mean admitting that giving children puberty blockers and chopping up their genitals maybe isn't such a good idea.
That's why he became a binge eater. Because he was so happy.